Socket outlet Or Fused Spur

[The Baker]

Socket outlet Or Fused Spur


On another forum the subject of fused spur verses three pin plug and single gang socket outlet is under discussion.

When a person is preparing to work on a gas boiler which method of connection do the electricians on this forum feel is most appropriate.


Personally I prefer a socket as this enables me to remove the boiler plug and connect my Socket & See Multi-functional Digital no-trip loop tester, model PDL 310 and take a reading to check if the Ohms reading present at this point is low enough to assist an adequate ionization current within the boiler.


I feel that the removal of the plug supplying electricity to the appliance give disconnection and isolation in one action, but some are of the view that doing so potentially removes the only known earth to that appliance.

I suggested that a flexible insulated earth wire if connected to the earth terminal of a three pin plug which is plugged into a nearby socket and an insulates crocodile clip connected to the boiler chassis would ensure a reliable temporary earth connection. (which I carry)


If the boiler suffering from lack of ionization due to a poor earth and pcb not receiving enough of a signal to verify the gas has been successfully ignited the boiler will lock out.


I am not a qualified electrician and do not delve into the back of a socket outlet of fused spur in other people’s houses as people can be very ungrateful if you uncover a wiring nightmare in the pattress.


I simple use in calibration equipment to get readings which if outside certain parameters prompt me to suggest the house holder get an electrician on the job.


Being able to determine if the earth is sufficient is important to my fixing a boiler with an intermittent fault.


Sorry if my question is long winded.


Any comments/suggestions gratefully received.

 

[The Baker]

 

[RF Lighting]

Personally I prefer to install an FCU as it allows the circuit to not have RCD protection. It also allows the boiler to be connected using fewer wires, and in my opinion is a neater and better job,

Having said that, there is absolutely no reason why a plug and socket arrangement can not or should not be used. It is a recognised method of electrical isolation, and can not fail unlike an FCU where contacts can weld. If the plug is unplugged you can physically see that all poles are disconnected. If specifically asked to install this I’d have no issues.

There is no problem removing the earth connection to the boiler as once the live is disconnected, there is no need for it to be earthed.

 

[The Baker]

Excuse my lack of knowledge. whats does FCU stand for.

 

[bernardgreen]

check if the Ohms reading present at this point is low enough to assist an adequate ionization current within the boiler.

Does the ionisation current flow out of the boiler on the Earth wire ?

FCU = Fused Connection Unit

 

[Harry Bloomfield]

Excuse my lack of knowledge. whats does FCU stand for.

I think it was supposed to represent a double pole fused spur unit. The fuse would be completely unnecessary, if the boiler was on its own 6amp MCB circuit. A plug and socket does make full isolation more certain, than a double pole switch - a switch can fail leaving the boiler still possibly connected to the mains.

A plug and socket, if that happens to be the only earth on the system, might put someone at risk when working on it - in exceptional circumstances. You have lots of copper pipes going all over the house and should one part make contact with a live conductor, the boiler and the entire system can become live.

I'm not sure whether or not the ionisation system actually needs a mains earth to the boiler, to function - I suspect not, so why would you need to test it?

 

[Taylortwocities]

Fused Connection Unit often (not absolutely correctly) referred to as a fused spur.

As RF says. Either is valid. I understand you might like a socket for your convenience, but what is your eventual plan? Are you going to impose sockets are fitted just for your testing convenience at every boiler?

How about you get yourself a proper multi function tester, theses have the option of test probes, then you can test on the mains input in the boiler?

 

[The Baker]

Thanks for the replies.

The boilers I work on require an eartconnection to enable the boiler pcb to recognise the gas /air has lit and the flame is established.

If I understand things correctly a heating/hot water demand to the boiler controller (pcb) which brings the fan on.
After a second or two the valve opens and the gas is pulled into the fan, mixed with air and forced out through the burner surface where it is ignited by a burst of sparks between the ign pin (spark electrode) and the burner face.

Immediately after the sparking ceases the controller feeds AC up the H T lead to the ign pin tip where upon it passes through the flame and changes from AC to DC which confirms to the controller that the gas is lit.
If sufficient ionization current is not present the boiler shuts off and needs to be re-set manually.

My tester does have an additional test lead with L, N, probes and an E croc but once I have established a possible low earth Ohms reading on my PDL 310 I need to know if the fault is within the boiler mains supply lead or within the fused spur.

If I still get a high Ohms reading I notify the responsible person and explain that I am not authorised to venture into there electrical circuits so they need to contact an electrician.

On a cold winters evening it can be very tempting to help people out by having a look behind the fused spur/socket outlet but the only thing I am willing to do is turn off the supply safely cut and isolate the cable leaving the suspect. Fused spur/socket outlet
and having fitted a new plug onto the boiler cable connect up to another socket outlet with an extension cable.

That's after I try other sockets on that floor.

Sorry about the long winded explanation but I know how difficult it can be to help people who did post up enough detail.

 

[sparkwright]

I think it was supposed to represent a double pole fused spur unit. The fuse would be completely unnecessary, if the boiler was on its own 6amp MCB circuit. A plug and socket does make full isolation more certain, than a double pole switch - a switch can fail leaving the boiler still possibly connected to the mains.

A plug and socket, if that happens to be the only earth on the system, might put someone at risk when working on it - in exceptional circumstances. You have lots of copper pipes going all over the house and should one part make contact with a live conductor, the boiler and the entire system can become live.

I'm not sure whether or not the ionisation system actually needs a mains earth to the boiler, to function - I suspect not, so why would you need to test it?

But don't most if not all manufacturers INSIST on a 3amp fuse to protect the boilers - and if this was not fitted, and there was some kind of fault, the manufacturers would completely void the guarantee?

 

[BS3036]

I believe there is a space for a 3A fuse inside a 13A plug though.

 

[sparkwright]

Yes, but H was making the point that a dedicated 6amp circuit may eliminate the need for a fuse in the double pole switch unit.

 

[EFLImpudence]

But don't most if not all manufacturers INSIST on a 3amp fuse to protect the boilers -

They might state one should be fitted but it should not be too protect the boiler which should and will have internal fuse(s).

How do boilers in Europe manage?

and if this was not fitted, and there was some kind of fault, the manufacturers would completely void the guarantee?

They might try if they are unscrupulous.

Should a 10mm² cable supplying a 60W lamp be protected by a 250mA fuse?

 

[sparkwright]

All true
but
I think I'd rather keep the manufacturer happy than go through a load of (expensive) aggro if there was any kind of fault.

 

[EFLImpudence]

Everybody does.

 

[EFLImpudence]

I am sure manufacturer's state such things because they think the UK regulations require them because they are available.